My betta Abraham falls to his side every time he stops swimming. This is my first betta so I have no idea what to do to help him.

Housing
What size is your tank?
2.5 gallons
What temperature is your tank?
78 degrees
Does your tank have a filter?
no, it did but it disturbed the water and Abraham didn't like it so I took it out last week
Does your tank have an air stone or other type of aeration?
no
Is your tank heated?
yes
What tank mates does your betta fish live with?
one ghost shrimp

Food
What type of food do you feed your betta fish?
omega one betta buffet pellets
How often do you feed your betta fish?
one or two pellets twice a day

Maintenance
How often do you perform a water change?
every three days
What percentage of the water do you change when you perform a water change?
50-100%
What type of additives do you add to the water when you perform a water change?
betta safe water conditioner

Water Parameters:
Have you tested your water?
no haven't got a test kit yet

Symptoms and Treatment

How has your betta fish's appearance changed?
no change
How has your betta fish's behavior changed?
he's laying on his side every time he stops swimming he's also not as active as he usually is.
When did you start noticing the symptoms?
today
Have you started treating your fish? If so, how?
no
Does your fish have any history of being ill?
no
How old is your fish (approximately)?
not sure He is a baby betta I got about three weeks ago from petco.

Can you post a picture? What I am guessing is SBD aka swim bladder disorder which happens... what size are the pellets? Being a youngin' and the fact he could have a smaller tummy it may be too much for him :)

Since he is a baby betta from a store there is a high chance he came to you sick... Their immune systems tend to be shot, as they can be between 4-8 weeks usually which can be a severe shock. Is there anything else? Gasping, heavier breathing, clamped fins etc? Is the spine curved?

Can you get a downward view/picture on him? Sometimes they grow out of it. I've had fry who have heavier bottoms or fall to their sides when they have a spine deformity... Usually they grow out of it but some don't. It doesn't seem to cause a problem as long as they are cared for really well, given a variety of healthy foods, and with chronic problems lower water usually helps (example: long VS tall tanks)

I do notice a bit of a "kink" per say, plus being a doubletail (a deformity, or severe mutation) he may have something genetic, especially if he doesn't show much for signs of illness or pain.

But first let's rule out everything first, but keep in mind he may just be a sick little doubletail.
Does he have or show the following:

Gasping?
Fuzz or slime anywhere on him?
Red or swollen gills?
Random spurts, or spasms, or darting across the tank?
Clamped fins?
White or transparent stringy, broken up poop?
Difficulty getting to the surface?
Swollen or sunken belly?

For his immune system to kick in more, I recommend a high diet... I use frozen foods and live foods. Depending on his size he can have live foods like adult brine shrimp. Otherwise use frozen bloodworms, mysis (you may need to chop them up more finely), brine shrimp, etc. it'll allow him a richer diet, which helps keep him healthy and will aid in his immune system along with growing.

See if you can get some Indian Almond Leaves... Bettas love them. And they act as a nice conditioner, and makes it more comfortable for them. Also see if you can get Stress Coat, and maybe Garlic Guard (or use minced garlic's juice)

No, I haven't seen any of those symtom's. Although, he is spending more time around the bottom of the tank only coming up for air/food. I'll definately try giving him fresh food to see how he does. Thanks so much for your help.